Magnet core



Nov. g0, 1934.= P. Roses? I MAGNET; coma Filed now z's, 1930 Ph l b gr Du use 2 Patented Nov. 20, 1934 i UNITED STATES PATENT OFFICE a MAGNET CORE Philip Norton Roseby, Liverpool, England, as-i signor to- Automatic Electric Company Limited, Liverpool, England, a British company Application November 28, 1930, Serial No. 498,69;

Great Britain November 30, 1929 The present invention relates to the construction of magnet cores and is particularly con,- cemed with cores which .are made from finelydivided material by the application 'of high pres 5 sure. Such cores find considerable application in loading coils of the type used on telephone lines where their special magnetic properties are particularly advantageous. Where a nickel-iron aly is used as the basic magnetic material as has 10 been general practice, difliculties are experienced in securing a core with both mechanical and magnetic-properties satisfactory. Thus after pressing has taken place annealing is desirable in order to give the core the most satisfactory mag- 1 5 netic properties, but .this annealing process is liable to ruin the insulating properties of the core According to the invention this difilculty is largely overcome by the addition to the finely divided alloy of a suitable proportion, for instance about 6% of calcined magnesia which may conveniently be made in powder form. This addition of calcined magnesia which may replace the proportion of iron powder sometimes employed permits annealing to be effected after pressing 5 since it does not --lose its insulating properties at high temperatures and thus it is possible by anhealing after pressing to restore the magnetic and mechanical properties which may have been somewhat prejudiced by this operation.

finely-divided particles of magnetic material having one dimension substantially longer than the others are arranged substantially parallel with their longer dimension in the same direction as the magnetic fieldgenerated during the subsequentuse of the core.

According to a further feature ofthe invention short lengths of finely drawn magnetic materialeach covered with a film of insulating material are arranged to be substantially parallel ,to

one another and are then subject to high pressure to cause them to agglomerate.

' The invention'will be better understood from the following description of one method of preeparing loading coils in accordance with the improved process, reference being had to the accompanying drawing. Nickel-iron wire of suitable composition is chopped into short lengths as described in my application Serial .No. 424,738 filed 30th January 1930, and is then annealed at approximately .650 C. for three hours. It is then cleaned with dilute hydrochloric acid and after washing, the particles are provided with an insulating coating by treatment with phosphoric According to another feature of the invention.

with approximately 3% calcined magnesia and .are then treatedwith varnish formed of a synthetic resin preferably that known under the registered trade name Bakelite." The powder thus prepared is then mixed with a further 3% of magnesia and is then in a form for transfer to the mould.

'Referring now to the drawing the apparatus used for filling the mould in the required manner will b described. The various elements are con- 6 veniegtly mounted on a base plate 1 which serves 'to a co odate a small electric motor 2 which by means of worm gearing 3 drives the mould a which is mounted so as to be capable of rotation. The required quantity of prepared powder for forming a complete core unit is placed inthe hopper 5 which is supported by an uprightbracket 6 and carries a smallrubber wheel 7 which runs on the mould 4 and is therefore rotated thereby. The wheel 7 is arranged to drive a small rake in the interior of the hopper for the purpose of agitating the powder and distributing it evenly into the mould. The amount of powder which flows out is controlled by the sliding door 8 the position of which is adjustable by means of the rack and pinion gear 9 controlled by the thumbscrew 10; The alignment of the particles is effected by the permanent magnet 11 preferably of cobaltst'eel which is adjustably mounted in an inclined position as shown and is supported by the vertical bracket l2. This bracket is adapted to be given vertical movement by means of suitable gearing contained in the box -13 and may be clutched by means of the control handle 14 to this gearing which is driven by the motor 2. Ac-

cordingly by suitable adjustment of the delivery of powder by means of the thumbscrew 10 it is" possible to arrange that as the mould fills up the ffimagnet 11 will be gradually raised at such a speed 1 as to maintain the most favourable position with regard to the surface of the powder for exereisin the maximum aligning eifect.

This effect could be enhanced if desired byv some arrangement for shaking the mould but since it is falling from the hopper such an ar- 10 rangement will probably not be necessary.

The subsequent operations in the formation of a core ring may follow usual practice except that after pressing has taken place the magnetic prop V erties of the ring may be improved somewhat by s annealing without impairing its insulating properties or mechanical strength. g

Accordingly the invention constitutes an advan'ce in loading coil construction whereby the 5:; acid. The insulated particles are then mixed core rings are'endowed with improved magnetic 11a in loading coils and the like in which short lengths of finely drawn nickel-iron wire are fed into an annular mould and are subjected to the effect of a strong magnetic field extending circumferentially so as to cause the particles to align themselves with their longer dim ion in the same direction as the magnetic field 3. The method of making magnet cores which consists in treating finely divided particles of magnetic material with a proportion of calcined magnesia, insulatingthe mixture with insulating varnish, treating the particles with a further proportion of calcined magnesia and then subiecting the mass to high pressure after which it is annealed.

a. The method of making magnet cores which yconsists in treating finely divided particles of inagnetic material with a 3% mixture of calcined magnesia, mixing the treated particles with an insulating varnish, treating the particles with a further 3% mixture of calcined magnesia and then binding the whole together into a homogeneous mass under heat and pressure after which it is annealed.

5. A process for making magnet cores in which 6. The method of making magnet cores which.

consists in treating short lengths of magnetic particles in one stage with calcined magnesia and in another stage with an insulating varnish, then subjecting the particles to a magnetic field to cause them to align themselves with their larger dimension inthe same direction as the magnetic field, after which they are subjected to pressure to bind them together and are finally annealed.

7. The method oi. making magnet cores which consists in treating short lengths of nickel-iron particles with a mixture of calcined magnesia to insulate them from one another, the particles with a binder of insulating varnish, then subjecting the particles to a magnetic field so that they are arranged substantially parallel with one another, after which the mass is subjected to pressure and then annealed.

8. A; method of making magnetic cores from finely comminuted core material which comprises mixing the comminuted core material with insulation, moulding the mass to the desired form and subjecting themass to the action of a magnetic field while moulding.

P NORTON ROSEBY. 

